Add additional context to queueable notification middleware method

[AndrewMonty]

I want to apply middleware to my queueable notifications, but only for specific channels and/or users. For example; no middleware for database notifications, but apply a rate limiter to email and sms notifications - unless the notifiable is an admin.

My suggestion is to pass $notifiable and $channel to the middleware() method on queuable notifications, similar to how withDelay works.